Physiologic Methods

what is immittance audiometry

important audiologic tool that is sensitive in detecting middle ear disorders, useful in differentiating cochlear from retrococh disorder, and helpful in estimating degree of peripheral hearing sensitivity and cross checks pure tone audiometry

what are three acoustic immittance measures

tympanometry, acoustic reflex threshold (ART) and acoustic reflex decay (ARD)

what are the two parts of tympanometry

equivalent ear canal volume and static compliance

three parts of acoustic immittance

admittance (compliance), impedance, and immittance

what is admittance (compliance)

ease with which energy will flow through middle ear

what is impedance

resistance to the flow of energy through the middle ear

what is immittance

general term encompassing both admittance and impedance

if the middle ear system is normal, will sound energy flow efficiently into cochlea?

yes, but if not, energy flow to the cochlea will be reduced

how does high impedance affect movement

reduced movement of the eardrum and ossicles, less sound energy getting into cochlea

what is a way of assessing sound energy flow through outer and middle ears to the cochlea (how well tm and ossicles are moving)

immittance audiometry

What is tympanometry?

physiological measure of middle ear function

three things that defines tympanometry (not instruments)

dynamic measure of acoustic immitance as a function of changes in airpressure in ear canal, can identify physical changes associated with ME, and determines whether there is a possible conductive component to hl

what is the instrumentation for tympanometry

1) rubber tip is placed around a probe that includes a mini speaker and mic, 2)an air pump creates either a pos or neg air pressure within canal, 3) mic detects change in sound pressure level

when does the tympanic membrane vibrate most efficiently?

when the pressure on both sides is equal

what happens when the pressure on both sides of the membrane is equal

most of the sound energy will pass into the cochlea and the mic will detect less sounds in the ear canal

for amiddle ear with normal function, where will peak appear on the graph

near 0 daPa

what is tympanic peak pressure

the pressure at which the peak of the tympanogram occurs and is assumed to be the point at which pressure in ear canal = middle ear pressure

what variables make up a tympanogram

ECV, static compliance, and pressure (positive and abnormal negative)

where is normal pressure for adults

-200 to +100

true or false, with a type C tympanogram, the ear and ossicles are NOT moving

false. ear and ossicles ARE moving, but ear drum is sucked in so issues with pressure

what is compliance

tells us how mobile the eardrum and ossicles are

what is the normal range for static compliance

.3 - 1.6/2 cc

if static compliance is below .3, what happens

ossicles moving too little, hypomobile

As ?

stiff, shallow wave, low compliance (less than .3)

Ad?

too tall, too mobile, hypermobile (above 1.6/2.0), high compliance

with someone with Ad tympanogram, what may they have

broken ossicular chain, weak eardrum, connective tissue disorders

true or false, with any of these tymps you will always have hearing loss

false, you can have normal hearing

what is ECV

allows us to check for type B tymps

why is ECV important

Accurate measure of static compliance depends on accurate estimation of ECV

If a pressure seal cannot be obtained, an estimation of equivalent volume can clue to the cause

norm ECV for kids and adults

kids=.4-1.0 cc

Adults = .6-2.5 cc

what does low volume ECV mean

Probe tip against cerumen, probe tip against ear canal wall

high volume ECV

Possible tympanic membrane perforation

Patent pressure equalizing tube (PE Tubes)

what are the five different tympanograms

A, As, Ad, C, B

what is type A tympanogram? (list it out)

indicates normal eardrum and ME function, normal pressure and compliance, normal peak

what is a type As tympanogram

shallow, stiff and small, has a peak but small

In the type As tymp, what is normal

ECV

As has decreased or increased impedance through the middle ear system?

increased impedance

pathologies associated As

tympanosclerosis, ossicular fixation, otosclerosis

Ad tympanogram

d=dislocation, really tall curve and mobile

Type B tymp

ECV can be too little just right or too high, no mobility so flat peak

does B have any mobility or pressure reading?

no, just ECV

small ECV for type B

wax or swimmers ear

normal ECV type B

possibly fluid (OM)

high ECV type B

perforated eardrum

what is middle ear effusion

fluid without infection

type C tympanogram

abnormal pressure, THE ONLY one with pressure issues (eustachen tube dysfunction)

what is an acoustic reflex threshold

softest loud sound that causes reflex to engage

what is an acoustic reflex

Reflex is an involuntary response to some external stimuli

what can an acoustic reflex tell an audiologist

provide informationabout site of lesion (cochlear vs. retrocochlear)

what two muscles are involved in operation of ME

tensor tympani and the stapedius muscle

three things about stapedius

Innervated by VIIth nerve (facial)

Connected to posterior side of stapes

Sole muscle responsible for acoustic reflex in humans

3 things about tensor tympani

Innervated by VAGUS nerve (Vth)

Connected to malleus

In some animals this muscle is responsible for acoustic reflex (not us)

When a sound is sufficient intensity

it will elicit the middle ear reflex

in humans, when a sound of sufficient intensity happens, the

stapedius muscle contracts and stiffens tymp membrane and ossicular chain

true or false, you have to do tympanometry before reflex

true

instrumentation for measuring acoustic reflex threshold

Rubber tip is placed around a probe that includes a miniature speaker and a microphone, speaker emits a pure tone, An air pump maintains a constant pressure in the canal, A second speaker is used to play a loud tone to stimulate the middle ear reflex, The mic detects the change in sound pressure level (dB SPL)

When a signal of intensity is presented to the rightear, a stapedius reflex

will occur in BOTH ears (ipsilaterl and contra)

if both reflexes aren't occuring at the same time, what pathology

neurological issue

frequencies we test for reflexes

500, 1000, 2000, 4000 Hz

how big of a deflection for a SURE reflex?

.03

normal dB ranges for acoustic reflex thresholds

0-100 dB, most 85

explain the pathway of the acoustic reflex arc

Sound conducted through outer and middle ear

Sound reaches cochlea and is conducted to 8th nerve Impulses received by cochlear nucleus in brainstem

Impulses passed to superior olivary complex in brainstem

Facial nerve innervates the stapedius muscle and impulses cause stapedius muscle to contract

true or false, abnormalities only in specific locations in the acoustic reflex arc can alter characteristics of the acoustic reflex

false, at any location

why does contralateral reflex typically have to be louder

cause it has to travel across the brain

when there is a conductive pathology, reflexes are

usually absent

acoustic reflex test is a ? (what threshold)

SUPRAthreshold test

what is a acoustic reflex decay

A measure of whether a reflex contraction is maintained or dies out during continuous stimulation

significant amounts of decay in lower frequencies can possibly be

lesions of aud nerve/brainstem

how is reflex decay measured

sustaining a tone at 10dB above ART for 10 seconds

if line is stagnant for decay

than stapedius didn't get tired

if initial response stays below ?

.5, it's negative decay (aokay)

positive decay is

can't hold reflex, lose stamina of reflex, could show you have a TUMA, lose over half of initial response by halfway point

Hz that you do decay at

500 and 1k

contralateral and ipsilateral tests, can they be used for decay?

yes, help locate lesion

what is an OAE

Sounds generated in the cochlea that can be measured in the ear canal with a mini mic

OAE arise from

the outer hair cells (amplifiers) of the cochlea

Healthy OHCs are necessary to produce OAEs

can one of absent OAE and good hearing

yes

is OAE a threshold test?

no, just tells us if hair cells are working

if one passes the OAE, typically won't have worse than

mild hl

true or false, OAE tests aud nerve

false, hair cells

people OAEs commonly used for

kids, babies, fakers

what are the two major types of otoacoustic emissions

spontaneous and evoked emissions

two important evoked emissions

transient OAE and distortion product OAE

TEOAE

broad range of frequencies

DPOAE

Most commonly used OAE, looks at frequency to frequency

Gives a cleaner picture of outer hair cells, emissions elicited by presenting two stimulus tones (f1 and f2)

if tm is perforated, than equivalent ear canal volume will

include ME space

tympanometry looks at

outer and ME

what makes a good test

high sensitivity and specificity

parts of measuring OAEs

Probe placed in ear canal contains miniature loudspeaker to present the evoking stimulus, tiny microphone

Computer equipment digitally analyzes the emissionresponse

Signal averaging is used to reduce the background noise in relation to the emission

Noise sources include room noise, body noise and equipment noise

before an OAE, you should

do a tympanometry test, so this means if you are doing an OAE your OE and ME is likely normal

if OAEs are present with sensorineural hearing loss, then

outer hair cell function is intact and the site of the disorderis retrocochlear

Absent OAEs with sensorineural hearing loss confirm

cochlear pathology but do not rule out the possibility ofretrocochlear involvement

OAEs add the what other info

Ability to distinguish between cochlear (sensorineural)and neural (retrocochlear) disorder Objective screening of auditory system function, particularly in the 1000 - 4000 Hz range, useful in infant hearing screening

Provides information about the cochlear status and an estimate of hearing status of individuals who are unable/unwilling to provide reliable behavioral responses to auditory stimuli

true or false, OAEs provide the ability to monitor changes incochlear function over time

true, especially in cases of noise exposure or ototoxic